Display apparatus may employ any of a wide range of technologies. Some non-limiting examples are plasma displays, liquid crystal displays (LCDs), cathode ray tube (CRT) displays, organic light emitting diode (OLED) displays, projection displays that use any of various light sources in combination with various spatial light modulation technologies, and so on. Displays may be of a wide variety of types used in any of a wide variety of applications. For example, the term display encompasses without limitation apparatus such as: televisions, computer displays, media player displays, displays in hand-held devices, displays used on control panels for equipment of different kinds, electronic game displays, digital cinema displays, special purpose displays such as virtual reality displays, advertising displays, stadium displays, medical imaging displays, and so on.
Different displays may have different capabilities in areas such as: black level, maximum brightness (display peak luminance), color gamut, and so on. The appearance of displayed images is also affected by the environment in which a display is being viewed. For example, the luminance of ambient lighting, the color of ambient lighting and screen reflections can all affect the appearance of displayed images.
With the increasing availability of high-performance displays (e.g. displays that have high peak luminance and/or broad color gamuts) comes the problem of how to adjust images for optimum viewing on a particular display or type of displays. Addressing this problem in simplistic ways can result in noticeable artifacts in displayed images. For example, consider the case where an image that appears properly on a display having a moderate peak luminance is displayed on a target display having a very high peak luminance. If one expands the luminance range of the image data to take advantage of the high peak luminance of the target display, the result may be poor due to objectionable artifacts that are rendered apparent by the range expansion. Artifacts may include, for example, one or more of banding, quantization artifacts, visible macroblock edges, objectionable film grain and the like. On the other hand, if the image is displayed on the target display without range expansion, no benefit is gained from the high peak luminance that the target display can achieve.
There is a need for apparatus and methods for processing and/or displaying images that can exploit the capabilities of target displays to provide enhanced viewing while reducing or avoiding undesirable artifacts.